Prior art structures exist for use in converting a regular pickup or flatbed truck into a dump truck. These prior art structures have relative structural complexity problems that may influence their practical value.
For example, some conventional structures act to lift the existing body of the truck, and require major modifications to the truck body structure. The structural and ride characteristics of the truck are affected. Certain other prior art structures use a central hydraulic cylinder which results in stability problems during the dumping operation.
In other cases, such as the structures shown in Dingler, U.S. Pat. No. 3,833,261 and Hill et al., U.S. Pat. No. 4,139,236, two hydraulic cylinders have been provided, but the ride characteristics of the truck worsen when the body of the truck is being lifted. In other prior art structures, where a bed liner is provided and two hydraulic cylinders were used, a modification was made in the truck body. Using two single-acting cylinders avoids the control complexity and safety concerns of using two double-acting hydraulic cylinders. Also, using two double-acting cylinders results in wasted space in the truck.
Another prior art structure (Anthony, U.S. Pat. No. 2,685,475) shows two hydraulic cylinders hinged on a common pipe or shaft in tandem on the front of the truck bed. But this design results in wasted space in the front of the liner.
Another prior art structure (Anthony, U.S. Pat. No. 2,684,864) shows a bed liner using two hydraulic cylinders (either double-acting or single-acting) that are partially disposed in front of the truck wheel wells and use separate hydraulics to operate the cylinders; this structure requires a separate bottom frame that is attached to the bottom floor of a pickup truck creating unusable space under the liner. The space occupied by the hydraulic cylinder from the front to the back on each side is unusable for other purposes. Also the hydraulic components occupy space in front of the insert container on the floor of the flatbed. This creates another unusable space adding to the loss of carry-on volume.